1. Field of the Invention
The present invention relates to drive circuits. More specifically, the present invention relates to drive circuits used for write heads for tape recorders and the like.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
In many circuits of a computing system, power dissipation is a significant concern. For example, in tape units, a need has been recognized recently for small tape products. However, in small tape units, little or no space is available for cooling fans. Pockets of thermal energy or hot spots are created which are deleterious to the circuitry of the unit. Hence, there has been an ongoing effort to reduce the power dissipated by the write driver circuits of small form factor tape units to minimize the heat generated thereby.
A conventional write driver uses open-collector type drivers to generate the write current pulse through the write head. Bidirectional write current pulses are generated by alternating the pulses to two bipolar write drivers. Each time a write pulse is sent to a write driver, the current through the write driver will be at least twice the current through the write head. This current is equal to the current through the resistors. While this approach is very fast, it dissipates a substantial amount of power.
An alternative design uses complementary metal-oxide semiconductor (CMOS) field effect transistors (FETs) in an H configuration. In this architecture, bidirectional current through the write head is controlled with alternating pulses through four FET devices. Power dissipation is half that of the above design. However, the parasitic capacitances of the FET devices cause the drivers to be significantly slower than the bipolar design above.
Thus, a need remains in the art for an improved write driver effective in small form factor applications. Specifically, there is a need in the art for a write driver design which utilizes the H configuration for lower power consumption and bipolar devices for faster switching.